Projection and Evaluation of the Land-Atmosphere Coupling Strength over China by CMIP5 Models

The ensemble mean summer land-atmosphere coupling strength of eleven models from the CMIP5 (Coupled Model Intercomparison Project, phase 5), performing the historical run in China, is calculated. The results show that the strength is relatively high in Huabei and Inner Mongolia, located in the semi-arid area, and the result in West China, located in the arid area, is second strongest. The lowest strength regions are the humid areas of eastern Northeast China, the middle and lower reaches of the Yangtze River, and Southwest China. Comparison of the ensemble mean with results calculated from NCEP and ERA-40 (European Centre for Medium-Range Weather Forecasts 40-Year Reanalysis) data shows high consistency. Next, the ensemble mean of the CMIP5 historical run and three RCP (Representative Concentration Pathway) runs (RCP2.6, RCP4.5, and RCP8.5) are used to predict the change in the strength of summer land-atmosphere coupling in China. The results show, compared to the historical run, the strength increases in the humid area of southern China, induced by higher evapotranspiration caused by higher temperatures. Meanwhile, the strength reduces in the Tibetan Plateau and semi-arid area of Inner Mongolia, induced by a reduction in the land-atmosphere coupling index caused by a reduction of evapotranspiration amplitude. The arid area of Xinjiang shows increasing strength in the RCP2.6 and RCP4.5 runs, but decreasing strength in the RCP8.5 run. This result is caused by enhanced vapor advection in the high emissions scenario, which makes the relationship between local evaporation and air humidity weaker. There is a higher degree of confidence in the prediction results in southern China and in the RCP4.5 run.